Does anyone know if there's any software out there that will allow me to "simulate" the Step 7 software I write on my PC without having to download to a PLC??

I'm sure I heard about some once upon a time but it was ages ago...?

Many thanks for any help you can give me

Cheers

If you buy the Profeesional package it comes with a PLC simulator
S7-PLCSIM Professional 2006 SR4 V5.4 + SP1 the current one.
Not sure but I think you can upgrade your existing packae to Pro by purchasing an upgrade lisence from Siemens.

Wow, I thought that maybe Siemens had changed their policy for downloading demo's of their software, but I am afraid that it is not the case.
That link is to SP1 for PLCSIM v5.4
In other words, it requires that PLCSIM is installed already.

To get demo versions from Siemens you normally have to contact them personally. Apart from that there is normally no fuzz about it.

Does PLCSIM do communications to outside devices ? ie, can I run Wonderware / iFix on the same PC or talk to PLCSIM via MPI / Profibus / Ethernet on another PC.

With PLCSim V5.4, it now has access points to support other communication paths besides MPI. I know for a fact WinCC and WinCC flexible can communication with PLCSim V5.4 using the access points, but not sure about the other brands. If you can point your Wonderware / iFix to the correct PG/PC interface for PLCSim then you could use it with those SCADA packages.

http://www.trysim.de/ this is the one I have, you can simulate the machine not just the code, the parts move and you have control over the speed and everything and you can crash it... just like in real life